Microstructure and Post-Irradiation Annealing Behavior of 20% Cold-Worked 316 Stainless Steel

2000 ◽  
Vol 650 ◽  
Author(s):  
J. I. Cole ◽  
T. R. Allen ◽  
H. Kusanagi ◽  
K. Dohi ◽  
J. Ohta
Keyword(s):  
Stainless Steel ◽  
Cold Work ◽  
Microstructural Development ◽  
Dislocation Loops ◽  
Annealing Behavior ◽  
Post Irradiation ◽  
316 Stainless Steel ◽  
Dose Rates ◽  
Cold Worked

ABSTRACTMicrostructural examination and in situ post-irradiation annealing studies were carried out on 20% cold-worked 316 stainless steel (SS) hexagonal duct material following irradiation in the reflector region of the EBR-II reactor. Stainless steel hexagonal ducts were used to house reactor subassemblies and provide a valuable source of information on irradiation behavior of reactor structural materials at lower dose-rates (on the order of 10-8 dpa/sec) than previously examined. The microstructural development of samples irradiated to doses of 1, 20 and 30 dpa is examined, while the post-irradiation annealing behavior of a sample irradiated to 20 dpa is described. Annealing studies were performed at 370 and 500°C to examine the kinetics of radiation damage recovery as a function of annealing temperature. The initial (pre-annealed) microstructures consists of a substantial density of irradiation induced chromium-rich M23C6 and M6C carbides which form both on the grain boundaries and within the grain interiors. Recovery of the cold- work is evident in the 1 dpa sample while samples irradiated to 20 and 30 dpa possess dense populations of voids and dislocation structures consisting of networks of line dislocations and faulted dislocation loops. Results indicate that post-irradiation annealing of the samples at 370°C for 1 hour has little effect on the microstructure, while further annealing at 500°C for 1 hour results in void shrinkage, the formation of small cavities, and a reduction in the dislocation loop and network density.

scholarly journals Mechanical Properties of 20% Cold-Worked 316 Stainless Steel Irradiated at Low Dose Rate

2002 ◽  
Author(s):  
Todd R. Allen ◽  
Hanchung Tsai ◽  
James I. Cole ◽  
Joji Ohta ◽  
Kenji Dohi ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Dose Rate ◽  
Work Hardening ◽  
Low Dose ◽  
Dose Range ◽  
Total Elongation ◽  
316 Stainless Steel ◽  
Dose Rates ◽  
Low Dose Rate ◽  
Cold Worked

To assess the effects of long-term, low-dose-rate neutron exposure on mechanical strength and ductility, tensile properties were measured on irradiated 20% cold-worked Type 316 stainless steel. Samples were prepared from reactor core components retrieved from the EBR-II reactor following final shutdown. Sample locations were chosen to cover a dose range of 1–47 dpa at temperatures from 371–385°C and dose rates from 0.8–2.8 × 10−7 dpa/s. These dose rates are about one order of magnitude lower than those of typical EBR-II in-core experiments. Irradiation cuased hardening, with the yield strength (YS) following approximately the same trend as the ultimate tensile strength (UTS). At higher dose, the difference between the UTS and YS decreases, suggesting the work-hardening capability of the material is decreasing with increasing dose. Both the uniform elongation and total elongation decrease up to the largest dose. Unlike the strength data, the ductility reduction showed no signs of saturating at 20 dpa. While the material retained respectable ductility at 20 dpa, the uniform and total elongation decreased to <1 and <3%, respectively, at 47 dpa. Fracture in the 30 dpa specimen is mainly ductile but with local regions of mixed-mode failure consisting of dimples and microvoids. The fracture surface of the higher-exposure 47 dpa specimen displays significantly more brittle features. The fracture consists of maily small facets and slip bands that suggest channel fracture. The hardening in these low-dose-rate components differs from that measured in test samples irradiated in EBR-II at higher-dose-rate. The material irradiated at higher dose rate loses work hardening capactiy faster than the lower dose rate material, although this effect could be due to compositional differences.

Effect of recrystallization on degree of sensitization in nickel free austenitic stainless steel

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sourabh Shukla ◽  
Awanikumar P. Patil ◽  
Ashlesha Kawale ◽  
Anand Babu Kotta ◽  
Inayat Ullah
Keyword(s):  
Stainless Steel ◽  
Thermal Aging ◽  
Thermomechanical Processing ◽  
Cold Work ◽  
Austenitic Stainless Steels ◽  
Content Type ◽  
High Deformation ◽  
Strain Induced Martensite ◽  
Degree Of Sensitization ◽  
Cold Worked

Purpose Effect of grain size on degree of sensitization (DOS) was been evaluated in Nickel free steel. Manganese and nitrogen contained alloy is a Ni-free austenitic stainless steels (ASS) having type 202 grade. The main purpose of this investigation is to find the effect of recrystallization on the DOS of stainless steel after the thermo-mechanical processing (cold work and thermal aging). Design/methodology/approach In the present investigation, the deformation of 202 grade analyzed using X-ray diffraction (XRD) and microstructural testing. Optical microstructure of Ni-free ASS has been done for cold worked samples with thermally aged at 900°C_6 h. Double loop electrochemical potentiodynamic reactivation test used for findings of degree of sensitization. Findings Ni-free ASS appears to be deformed more rapidly due to its higher stacking fault energy which gave results in rapid transformation from strain induced martensite to austenite in form of recrystallized grains, i.e. it concluded that as cold work percentage increases more rapidly recrystallization occurs. XRD results also indicate that more fraction of martensite formed as percentage of CW increases but as thermal aging reverted those all martensite to austenite. So investigation gives the conclusion which suggests that with high deformation at higher temperature and duration gives very less DOS. Originality/value Various literatures available for 300 series steel related to the effect of cold work on mechanical properties and sensitization mechanism. However, no one has investigated the effect of recrystallization through thermomechanical processing on the sensitization of nickel-free steel.

Sign in / Sign up

Export Citation Format

Share Document